Software for Individualbased Models

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Software for Individual-based Models

• Problems
• Solutions
• Software Platforms
• Testing Methods

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What Software Challenges Do IBMs Present?
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Why is Software So Important for IBMs? (1)

• Even simple IBMs can be complex
• Many kinds of entities
• Virtually infinite model states and execution
  pathways
• Software design becomes important

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Why is Software So Important for IBMs? (2)

• Software is just another implementation of a
  model - NOT TRUE
• Software must allow us to
• Observe the model from many perspectives
• Understand what happened and why

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Why is Software So Important for IBMs? (3)

• Quality control is a serious job
• Errors are inevitable yet rarely obvious

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Why is Software So Important for IBMs? (4)

• Standardization and Communication
• The more we use the same software tools, the
  easier it is to describe models completely and
  accurately

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Software Engineering(vs. programming)

• Selecting an appropriate platform
• Designing the softwares organization
• Providing observer capabilities
• Conducting a quality control program
• Conducting software maintenance
• ...

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Dealing with Software Challenges

• Select an appropriate, widely used platform
• Collaborate with software professionals
• Provide observation and analysis tools early
• Conduct a pervasive testing process

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Software Platforms
Repast
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Software Platforms

• Reduce effort
• Reduce errors
• Provide tools
• Observation
• Automatic experiments
• Standardize models enhance communication
• Provide a community

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Software Testing

• Bugs in IBMs are
• inevitable
• not obvious
• found only by looking hard
• (if not found) extremely expensive and
  embarrassing

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Software Testing Methods (1) Code Reviews

• Catch many typos and logical errors
• Encourage well-organized code
• software should be written for people, not
  machines

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Software Testing Methods (2) Spot Pattern Tests

• Catch widespread errors
• Are powerful with graphical output

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Visual Pattern Tests
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migrantLocX migrantPrevLocX (timeStepSize
(habVelX migrantRandomVelX) ) migrantLocY
migrantPrevLocY (timeStepSize (habVelY
migrantRandomVelY) )
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Testing Methods (3) Second Implementation

• The only (reasonably) reliable way to catch
  errors that happen only some of the time or to
  some individuals
• (which are very common!)

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Second Implementation of Submodels is Not Hard
Written formulation
Submodelprototype
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Second Implementation of Submodels is Not Hard
Written formulation
Complete software
Submodelprototype
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Second Implementation Example
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Software What We Can Do

• Plan and budget
• Share, develop, and support common tools